The surveillance of approximately 1500 patients with bladder cancer has been undertaken in eight collaborating institutions. Characteristics of the patients are recorded when they first develop their cancer and at each stage in their disease within a 5 year follow-up period. Simultaneously, various pathologic and cytologic characteristics are recorded, and together these will be correlated to determine which characteristics predict subsequent disease events so that treatment decisions can be placed on a more sound basis. The framework of this part of the study provides a setting for clinical trials of thio-tepa in selected patients with superficial cancer and of definitive radiotherapy instead of preoperative radiotherapy for selected patients with invasive cancer.